Process for stabilizing creosote oils by shock cooling and stabilized product



atent Ofiice PROCESS FOR STAEELHZTNG CREOfiOTE OILS-BY SHOCK (ZGGLENG AND STABILIZED PRODUCT John Vincent Savercool, Montviile, N. J., assignor to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York No Drawing. Application December 10, 1953 Serial No. 397,487

.5 Claims. (Cl. ll6149) tillates of coal gas tar and coke oven tar, and have been known and used for many years for a variety of purposes. The term creosote oils therefore, refers to a variety of oils of extremely complex chemical composition and physical properties, and these attributes vary markedly with the'source of the oil, the distillation process by which it was recovered and other factors concerning its history. For example, the coal gas tars and coke oven tars are usually distilled to produce at least two fractions, a light or low boiling fraction, a heavy or high boiling fraction, and sometimes a medium fraction as well, in addition to the pitch or tarry residue which remains in the still. The resulting oils are then often topped v or otherwise treated to recover a portion of certain selected types of compounds therefrom such as tar acids i. e. phenols, cresols, etc., tar bases, i. e. heterocyclic nitrogen bases, a naphthalene fraction, etc.

The oils marketed as creosote oils may be constituted of all or part of the original distillate, or, as is often the case, they may be blends of distillates which have been treated in other recovery operations.

one of the largest and most important of which is for wood preservation by treatment of the wood with the creosote oil by suitable methods, which may include brushing, spraying, immersion, or the like, with or without the aid of vacuum or pressure treatments usually at elevated temperatures.

If the original distillation of the tar has been carried out to form a hard pitch, e. g. if the tar has been heated at temperatures 'up to about 355 C. or above to remove a large percentage of the high boiling oils from the residue, the proportion of high boiling crystallizable compounds in theresulting heavy and medium oils will be high, and such compounds may also be present to some extent in the lighter oils as well.

Such high boiling low volatile constituents are the least soluble fractions of the creosote oil and hence crystallize out of solution upon cooling of the oil to appropriate temperatures. These crystallizable compounds occur as mixtures of a variety of compounds including anthracene, carbazole, phenanthrene and the like. They are usually colloquially characterized as anthracene salts, and, when in solution in the creosote oil, are valuable constituents in wood preservation, it being generally recognized in the industry that the low volatile, high boiling constituents provide the longest and best protection in preserving wood poles, ties and the like.

Many creosote oils, especially oils containing high percentages of crystallizable compounds, although fluid when freshly prepared, often precipitate a portion of the crystalline anthracene salts, on storage or shipment under These exv tremely complex mixtures are sold for a variety of uses,

prevailing industrial conditions, especially in th'ewin'tei months when temperatures are low. This crystal sepa ration is extremely troublesome and costly because it complicates pumping of the oils and emptying'oftank cars, and also occasions losses in total oil delivered diie to the fact that a portion of the initially measured oil 'is deposited as a crystalline residue in the tank. Theseparated anthracene salts have a high melting point} con siderably above the temperature at-which creosot'e oil can readily be removed from tanks or cars. Practicably, they can be removed only by redissolving'in'creos'ote oil at a high temperature with sufficient agitationandffor a sutficient time to efiect solution.

These difiiculties have led to many attempts in" the past to treat or clarify the creosote oils to preserve their liquidity. i

Creosote oils of the character described have been treated or clarified in the past to produce oils of higher liquidities by a number of methods based on crystallization and removal of the so-called anthracene salts, including storage for long periods during ,which the anthracene salts precipitated from the oil and settled to the bottom of the storage vessel. Another prior clarification method involved slowly cooling the ,oil inlarge agitated vessels equipped with internal cooling coilsyfol lowed by separation of the crystallized solids from the oil, usually by centrifuging. Another method utilized an outside heat exchanger with pump circulation to effect slow cooling of the oil. In still another method, the oil was passed through a tank or tower equipped with exterior cooling means and rotating side scrapers to remove the crystalsfrom' the walls of the tank, and the resulting crystal slurry was passed to a centrifuge to separate crystals from mother liquor. All of theseprocesses had the disadvantage of high cost, eitherforjstorage or for refrigeration and "separationof crystals, and 'entailed otherwise unnecessary loss to the consumer of these valuable salts from the creosote oils.

. It has long been known that in manycrystallization processes, very rapid or shock cooling often produces extremely fine crystals, and that such fine crystals tend to remain suspended in the mother liquor for longer periods than do larger crystals, that is, the finer crystals settle more slowly than do the larger ones, until, in the extreme case of colloidal size particles (generally characterized as particles of less than 0.1 micron in diameter), the particles remain indefinitely'suspendedf Therefore, in clarifying processes of the prior art, shock-cooling was studiously avoided, as the fine crystals were very difficult to remove either by filtration or settling processes.

It is an object of the present invention to provide a process for producing stable, free flowing, non-caking creosote oils.

It is another object of the invention to provide a process for producing stable, free flowing, non-caking creosote oils of high fluidity within the range of normal storage and shipping temperatures, without the removal of anthracene salts therefrom.

A still further object of the invention is to provide creosote oils containing finely divided anthracene salt" crystals in suspension, which crystals will'remain suspended during storage and shipment under normal industrial conditions to provide mobile, free flowing suspensions at temperatures above about 20 C. (68 F.).

A still further object of the invention is to provide stabilized creosote oils containing finely divided anthracene salts in suspension, which remain stable and substantially non-settling under conditions of temperature fluctuations below the limpid point of the oil.

These and other objects are accomplished according to my invention wherein creosote oils, containing anthracene salts which normally crystallize out on storage-at Patented June 10, 1958,

low temperature to produce large, crusty, fast settling crystals, are rapidly cooled (shock cooled) either batchwise or continuously at a rate sufliciently rapid to insure production of crystals whose maximum diameters are not more than about 15 microns.

The benefits of my invention are made possible by my discovery that if shock cooling is carried out at the particular rates specified herein to produce anthracene salt crystals of a maximum diameter of not more than about 15 microns, a stable creosote oil is obtained which remains mobile under all temperature conditions between about 20 C and the limpid point of the oil, if not more than about of crystals are present, and, at temperatures of about 15 C. and below, sets to a thixotropic structure having the appearance of a gel, which persists at further reduced temperatures and thus preserves the dispersed stability of the system at temperatures which would normally be encountered in the storage or shipment or such oil.

In carrying out the process of my invention, the creosote oil to be stabilized is brought to a sufliciently high temperature so that all salts are in solution, preferably to about C. above its limpid point. The oil is then uniformly cooled rapidly, preferably with agitation to assure uniform heat exchange, by any suitable cooling means, from a temperature above its limpid point to a temperature appreciably below its limpid point. The limpid point of creosote oil as the term is used herein, is the temperature at which the last crystals disappear when the oil is gradually heated from a lower temperature. The cooling rate employed in my process is sufficiently rapid to shock cool the oil and to insure formation of very fine crystals having diameters not exceeding about microns, with many crystals being considerably smaller, some perhaps even colloidal in size. The resulting shock cooled creosote oils usually have a macroscopic appearance of complete homogeneity and liquidity, no crystals being apparent to the naked eye. The crystals, however, are readily visible under the microscope at magnifications for example of l00 and may be filtered if suitable filter surfaces are used, for example, sintered glass or the like. The shock cooled oils are stable, non-settling dispersions of very fine crystals of anthracene salts in a stable oil phase.

Cresote oils which are adapted for shock cooling treatment according to my invention, to produce stable, fine crystal-containing oils, include the so-called light, medium and heavy creosote oils. My invention is particularly adapted for use in treating the heavier oils resulting from carrying tar distillations to harder pitches, and which oils thus have relatively higher percentages of components boiling at about 355 C. and above which tend to crystallize on cooling of the oil. While the oils contemplated for treatment according to my invention are extremely complex and have widely varying character istics, they may be defined generally as distillates of coal gas tar or coke oven tar or fractions or mixtures thereof having boiling ranges predominantly within the range between about 200 C. and about 400 C., and having specific gravities of between about 1.03 and about 1.14. Many of the light creosote oils distill completely within the range between about 200 C. and about 355 C., while others, such as the so-called medium and heavy oils, notatably the creosote oils from hard pitch distillations, may contain up to 50% of components distilling at 355 C. and above.

Such creosote oils, upon cooling to temperatures between about 10 C and about 60 C. may precipitate between about 0.5% and about 5% by weight (dry basis) of anthracene salts, i. e. crystals containing essentially anthracene, carbazole, phenanthrcne and the like, and usually precipitate between about 1% and about 3% of such crystallizable compounds. Oils which contain more than about 5% of components crystallizable in the above temperature range are not adapted for treatment accord- 75 tl g dificulties, the oils of my inventionset up to thixoing to my invention, as such oils, when shock cooled" set up thixotropic gel-like structures at normal atmospheric temperature and above. Oils containing less than about 0.5% of crystallizable anthracene compounds as defined, usually present little ditficulty with crystal separation so that treatment of such oils is usually not necessary. Accordingly, I prefer to use creosote oils which contain between about 0.5 and about 5% (dry basis) of anthracene salts crystallizable in the above temperature range. In general the quantity and chemical composition of crystalline material resulting from shock cooling and from ordinary slow cooling of the oils are substantially the same, other conditions being equal.

Shock cooling of the creosote oils may be effected according to my invention by any suitable conventional means that produces crystals of the indicated fineness, i. e. that effects the required rate and magnitude of temperature drop. Preferably a heat exchanger is used which provides for agitating while cooling the oil, and provides for scraping the cooling surfaces during the cooling process. Any suitable cooling medium may be used including water, brines, ammonia or other refrigerants. Other suitable cooling methods may be employed for example flash (vapor) cooling under vacuum, spray cooling in a chilled receiver, direct mixing with a refrigerant or the like.

The cooling rate is an important feature of my invention by which the desired crystal size is controlled, and this rate should be extremely rapid to induce formation of extremely fine crystals and to super cool the solution sufliciently to prevent their growth beyond a maximum of about 15 microns. For this purpose cooling rates of at least about 033 C. (054 F.) per second are used, preferably somewhat higher rates. For batch-wise operation, rates between about 1 C. and about 3 C. per second are especially satisfactory, while for continuous scale operation, rates of from about 035 to about 0.90 C. per second are especially satisfactory. The temperature range through which shock cooling is effected is from a temperature above the limpid point of the oil, to a temperature at least 10 centigrade degrees below its limpid point, final temperatures of from 15 to 25 C. or even higher usually being sufficient.

The resulting shock cooled creosote oils are stable liquids of homogeneous appearance which contain between about 0.5% and about 5% of microscopic crystals of anthracene salts having maximum diameters of about 15 microns, many crystals being considerably smaller, some possibly being even colloidal in size, the majority of crystals probably ranging in size between about 1 micron and about 15 microns. The shock cooled oils exhibit apparent viscosity characteristics higher than those of normally cooled samples of the same oil, the difference varying from zero at the limpid point temperature of the oil where the viscosity characteristics of shock cooled and normally cooled oils are the same (there being then no crystals to interfere) to much greater difierences at lower temperatures, the shock cooled oils usually setting up to thixotropic structures at temperatures below about 15 C. These structures are readily broken however, by stirring, or by heating to about 20 C., to again produce adequately mobile liquids which can readily be pumped in the usual way.

The shock cooled creosote oils remain stable, noncaking and substantially non-settling over prolonged pcriods, amply sufficient to insure stability during storage and shipment under normal industrial conditions. Neither agitation, such as shaking or vibration, nor heating to elevated temperatures below their limpid points, even with repeated cycles of such heating followed by cooling, destroys the stabilities of the shock cooled oils. At lower temperatures, such as are experienced in the fall and winter months, and which are the conditions which normally cause the gravest crystallizing and settropic gel-like structures which structure apparently serves to preserve the characteristics of the shock produced crystals at such low temperatures. Since the thixotropic structure can readily be broken by extremely mild heating (to 20 C., i. e. 68 F.) and as most creosote oil tank cars are, in any case, equipped with heating coils, this setting presents no ditficulties in unloading or pumping of the oil, but merely serves to further stabilize the oil at the more critical, colder temperatures it may encounter. My process of shock cooling, moreover, provides a creosote oil containing all of its normal constituents, including the valuable low volatiles, and, as a result, is superior in wood preserving efliciency to oils which have been specially treated to eliminate these valuable but troublesome crystallizing fractions.

The following specific examples further illustrate my invention.

EXAMPLE 1 Identical samples of a creosote oil having the following physical characteristics:

Specific gravity 38/15.5 C 1.083 Limpid point, deg. C 38.0 Washed salts (dry basis) at 25 C percent 2.5

Creosoters Distillation (A. W. P. A. A1-51):

Weight percent, dry basis to 210 0.3 235 11.4 270 33.6 315 47.6 355 71.1 Residue 28.1

to drop to room temperature (25 C.) over a period of 5 hours. This delayed cooling procedure produced crusty crystals of the same type as those contained in the oil as received resulting from crystallization on long storage.

SHOCK COOLING Ten additional portions of the hot (70 C.) creosote oil, each of 50 grams, were placed in test tubes having inside diameters of 32 mm., to about half fill the tubes. These test tubes with creosote oil were immediately immersed in a freezing mixture of solid CO and a light petroleum distillate (Atlantic 44 solvent) at 70 C.,

while stirring the creosote vigorously by means of a rod equipped with a perforated plate which scraped crystals from the sides of the tube as they formed. The test tubes and creosote samples were allowed to remain in the freezing mixture for 6 seconds after their limpid point temperature of 38 C. had been reached when the temperature of the creosote oil had dropped to about 25 C. (a cooling rate of about 2 C. per second), and were then removed from the mixture.

SETTLING TESTS Three 100 ml. samples of each of the delayed cooled and shock cooled creosote oils prepared as described above, were immediately placed in 100 ml. graduated cylinders and stoppered. One sample of each was stored for one week at 23 C., another set was stored for 3 weeks at this temperature, the third set was analyzed immediately, the other two after the indicated storage periods, to determine the proportion of solids in the top and bottom 50 ml. portions of the samples respectively. The solids determination was carried out by filtering top and bottom portions separately through 200 mesh sieves in the case of the delayed cooled oils, and through sintered glass crucibles in the case of the shock cooled oils, returning the filtrate through the filter at least once, using suction on succeeding filtrations after the first filtration had produced a mat of crystals on the filter surface. The crystals were then washed, first by slurrying in a container with 50 ml. of a light petroleum fraction, then filtering and again washing on the filter surface with an additional 15-20 ml. of petroleum to remove occluded mother liquor. They were then dried under vacuum at 60 C. Whenever the terms washed salts, dry salts, or dry basis as applied to the salts, are used herein they mean that the salts have been washed with a non-solvent organic liquid to remove occluded mother liquor and dried under vacuum substantially as described above.

Results of the settling tests are listed in Table 1 below:

Table 1.Pr0portions of crystals in top and bottom halves of delayed cooled and shock cooled creosote oils immediately after crystallization and after one and three weeks storage periods at 23 C.

Weight of Oil (g) Weight of Dry Salts (g) Delayed Shock Delayed Shock cooled cooled cooled cooled 54.0 58.1 0.0 1. 6 55.1 53. 3 3. 4 1. 4 Total 109.1 111. 4 3. 4 3.0 Three Weeks:

Microscopic examination of the shock cooled creosote oil above, revealed crystals having diameters ranging from about 1 micron to about 15 microns, typical diameters being about 10 microns.

EXAMPLE 2 SETTLING WITH SHAKING Two identical samples of a creosote oil having the following physical characteristics:

Specific gravity, 38/15.5 c 1,0 5 Limpid point, C 48.0 Washed salts at 25 C. (dry basis) percent 2.5

Creosoters Distillation (A. W. P. A. Al-5 1):

Weight percent,

dry basis to 210 10.7 270 43.4 315 61.6 355 82.0 Residue 17.4

heating the creosote oil above 58 C. above its limpid point) to insure solution of all the crystalline salts, then placing the container with the hot creosote oil in a large water bath at the same temperature. The temperature of the water bath and oil were then allowed to drop to room temperature (25 C.) the drop from the limpid point of the oil (48 C.) to 25 C. occupying a period of one hour.

A number of one hundred ml. samples of (A) the above oil as received, containing large crusty crystals, and of (B), shock cooled and (C), slow cooled creosote oils prepared from this oil were placed in 100 ml. graduated cylinders and'kept at room temperature (25 C.) for two days, then were shaken for 4 days at room temperature on a Burrell wrist action shaker. The samples were then allowed to stand quiescent for two additional days at room temperature, and then were divided into top and bottom 50 ml. portions and analyzed, as described in Example 1, for percent salts. The shock-cooled samples had set up to a gel structure shortly after preparation and had maintained this structure throughout the shaking test. Therefore, immediately before analysis the graduated cylinders were submerged for 2 minutes in water at 3E C. without shaking, to break the gel. All samples were treated in this manner for the sake of uniformity of treatment. Results of the analyses are given in Table 2 below.

Table 2.-Proporti0ns of crystals in top and bottom halves respectively of (A) normal, (B) "intermediate slow cooled" and (C) "shock cooled" creosote oils after settling, shaking and settling tests Weight of Dry Salts Weight of 011 (g) As Received (A):

It will be noted that substantially no settling took place in the shock cooled oil whereas in the oils as received and after slow cooling, all the salts had settled to the bottom half of the container and had formed a hard cake. Microscopic examination of the above shock cooled oils, revealed that the crystals had diameters ranging from about 1 micron to about microns, averaging I about 10 microns.

EXAMPLE 3 SETTLING WITH HEATING CYCLE shaking or mixing. Thereafter the samples were allowed Weight of Dry Salts "Weight of 011 (g.)

As Received (A):

p 54. 0 0. 0 Bottom. 57. 1 2. 9 Tot 111. l 2. 9

Slow Cooled The normal oil as received and the intermediate slow cooled samples had settled completely to a cake at the bottom of the cylinder. The analyses indicate that the shock cooled oil had settled slightly, but no visual evidence of this was apparent and no crystals were found on the bottom of the cylinder.

Microscopic examination of the above shock cooled oil revealed that it contained crystals ranging in size from about 1 micron to about 15 microns, averaging about 10 microns.

EXAMPLE 4 Samples of normal (delayed cooled) and shock cooled creosote oils of the oils of Examples 1 and 2 were subjected to Viscosity determinations at temperatures ranging from 12 C. to C. in a Stormer Viscosimeter equipped with a paddle rotor. The time in seconds required for 50 revolutions of the paddle under weight loads of 5, 7 and 30 grams was measured, with the results given in Table 4 below.

Table 4.--Viscosities of "delayed cooled and "shock cooled creosote oils OREOSOTE OIL, OF EXAMPLE 1 Shock-Cooled Delayed-Cooled Temperature of Test, Degrees 0.

5g. 7g. 30g 5g. 7g. 30g.

IL, OF EXAMPLE 2 *Weight insufficient to move paddle.

The above data indicate the differences in consistency of shock cooled and delayed cooled creosote oils, the shock cooled being considerably the more viscous. The differences are striking at temperatures below 15 C. where the shock cooled oils set up as thixotropic gels. At the other extreme, above the limpid point temperature, the viscosities of the two types of oils are the same, since no crystals are present to affect their fluidity. The temperatures at which the viscosities of shock cooled and delayed cooled oils (prepared from the same "original oils) become the same is the limpid point of the oil.

V EXAMPLE Shock'Cooled creosote oil was continuously prepared in an apparatus comprising a water jacketed brass condenser tube equipped with a rotating scraper having blades in close contact with the wallsof the condenser. During operation, water was passed through the jacket at 5-20 C. and the scraper was rotatedat a speed of 80-revolutions per minute. In four separate runs, the creosote oil of Example 1 was introduced into the bottom of the condenser tube and allowed to emerge at the fastest rate consistent with efllux temperatures of 15 to 25 C. to form many fine crystals within the oil. The experimental conditions employed in the four runs are given below in Table 5.

. Table 5 Water Oil Temp, C. Rate of Cooling Run No. temp, Rate, O. Grams/ Deg.

In Out Minute O./Scc.

Microscopic examination revealed that the crystals formed in the above treated oils had the same size (maximum about 15 microns), the same characteristic uniformity of dispersion through the oil, and the same viscosity and settling characteristics as those produced by batch shock cooling.

Viscosity characteristics of the above continuously prepared shock cooled oils measured in the manner described in Example 4, are given in Table 6 below.

Settling over one and two week periods at room temperature (25 C.), carried out as described in Example 1, is shown in Table 7 below for the four continuously shock cooledf oils.

Table 7 Settling Period Washed Salts, g. One Week Two Weeks Top Bottom Total Top Bottom Total While slightly more settling is shown by these runs than occurred in the shock cooled material prepared batch-wise from the same creosote oil, as detailed in Example 1, nevertheless, after 8 weeks standing at room temperature, samples from Run 4, which showed the most pronounced settling could be poured from the graduated cylinders without leaving a crystal deposit on the bottom of the cylinder.

1 0 EXAMPLE 6 A total of about 12,000 gallons of a creosote oil having the following physical characteristics Specific gravity, 38/15.5 C 1.073

Limpid point, deg. C 60.8 (141.5 F.)

Washed salts (dry) at 25 C ..percent.. 5.0

Creosoters Distillation (A. W. P. A. Al--51):

Weight percent,

dry basis Residue 18.9

was continuously shock cooled in a series of 22 runs of approximately /2 hour to one hours duration each, by passing the oil through a cooling chamber having a volumetric capacity of 0.0843 cubic feet (0.63 gal.), said chamber comprising an annular space between two concentric. cylinders of difierent diameters, the outer cylinder of which was water jacketed. The inner cylinder was equipped with paddle type rotating scraper-agitators having blades which continuously scraped the inner walls of the outer cylinder, and removed crystals rapidly and cleanly as they formed. Residence times, i. e.

(capacity of cooling chamber) rate of oil feed and cooling water temperatures were varied to effect cooling from initial temperatures between 126 F. (52.2 C.) and 171 F. (77 C.) to terminal temperatures of 78 F. (25.5" C.) to 95 F. (35 C.) at cooling rates varying from 0.78 F. per second (0.42" C. per second) to 436 F. per second (2.42 C. per second) as listed in Table 8 below.

Table 8.--Contmu0us cooling of creosote Oll Feed Temperatures. F. Cooling Feed Rate, Gals/min. Rate,

80 F. F./Sec.

In Out AT The resulting creosote oils had the visual appearance of homogeneous liquids. Filtration of a portion of the shock cooled oils however, revealed that they contained about 5% by weight (dry basis) of extremely fine anthracene salt crystals and no coarse crystals. Material from the several runs was passed to a common storage tank and mixed therein.

Several ml. portions of the above shock cooled creosote oil were placed in 100 ml. graduated cylinders which were then stoppered. One portion was analyzed immediately to determine quantities of salts in top and bottom halves of the sample, others were stored at 23 C. for periods of one, two and four weeks and then sub- 1 1 jected to salt determinations on the top and bottom 50 ml. portions with the results shown in Table 9 below.

While the above figures indicate that some settling had occurred, no crystalline deposits were found on the bottoms of any of the cylinders.

To test the stability of this oil under normal shipping conditions, approximately 10,000 gallons of the above blended shock cooled oil were loaded at 78 F. into a tank car in the Metropolitan New York area on a day when the ambient temperature was about 60 F. The car of oil was then shipped to Detroit, Michigan, where it was unloaded 10 days later, at an ambient temperature of 50 F. The oil thus shipped was free of coarse solids, and no settled salts or solids remained in the car after unloading. The tank car was clean and satisfactory for immediate reuse.

While the above describes the preferred embodiments of my invention, it will be understood that departures may be made therefrom within the scope of the specification and claims.

I claim:

1. As a new composition of matter a stable, non-calcing, macroscopically homogeneous-appearing creosote oil containing between about 0.5% and about (dry basis) of anthracene salt crystals having maximum particle diameters not exceeding about 15 microns and having the property of remaining substantially noncaking under conditions of temperature fluctuations below the limpid point of the'oil for indefinite periods at least sufficient to insure adequate suspension stability during storage and shipment under normal industrial conditions.

2. As new compositions of matter, stable, non-caking creosote oils having adequate pumping mobilities at temperatures of 20 C. and above, containing between about 1% and about 3% (dry basis) of anthracene salt crystals having particle diameters not exceeding about 15 microns and'having the property of remainingsubstantially non-caking under conditions of temperature fluctuations below the limpid point of the oil for indefinite periods at least suflicient to insure adequate suspension stability during storage and shipment under normal industrial conditions.

3. A process for preparing creosite oils containing in stable suspension between about 0.5% and 5% (dry basis) of anthracene salt crystals having maximum particle diameters not exceeding about 15 microns, having adequate mobilities at temperatures of about 20 C. and above, from creosote oils from which between about 0.5% and about 5% of crystals (dry basis) normally separate at temperatures in the range between about 10 C. and about C., which comprises decreasing the temperature of said creosote oil from a temperature above its limpid point; to a temperature of at least about 10 C. below its limpid point, at a rate measured from its limpid point temperature to said lower temperature, of at least about 0.3" C. per second whereby suspensions are produced having the property of remaining substantially non-caking under conditions of temperature fluctuations below the limpid point of the oil for indefinite periods at least suflicient to insure adequate suspension stability during storage and shipment under normal industrial conditions.

4. A batch process for preparing creosote oils containing in stable suspension between about 0.5 and 5% (dry basis) of anthracene salt crystals having maximum particle diameters not exceeding about 15 microns, having adequate pumping mobilities at temperatures of about 20 C. and above, from creosote oils from which between about 0.5% and about 5% (dry basis) of crystals normally separate at temperatures in the range between about 10 C. and about 60 C. which comprises decreasing the temperature of said creosote oil from a temperature above its limpid point to a temperature between about 15 C. and about 25 C. at a, rate measured from its limpid point temperature to said lower temperatures of between about 1 C. and about 3 C. per second whereby suspensions are produced having the property of remaining substantially non-caking under condi tions of temperature fluctuations below the limpid point of the oil for indefinite periods at least suflicient to insure adequate suspension stability during storage and shipment under normal industrial conditions.

5. A continuous process for preparing creosote oils containing in stable suspension between about 0.5 and 5% (dry basis) of anthracene salt crystals having maximum particle diameters not exceeding about 15 microns, having high mobilities at temperatures of 20 C. and above, from creosote oils from which between about 0.5% and about 5% (dry basis) of crystalline components normally separate at temperatures in the range between about 10 C. and about 60 C., which comprises decreasing the temperature of said creosote oil from a temperature above its limpid point to a temperature between about 15 C. and about 35 C. at

a rate measured from its limpid point temperature to said lower temperatures of between about 0.35 and about 090 C. per second whereby suspensions are produced having the property of remaining substantially non-caking under conditions of temperature fluctuations below the limpid point of the oil for indefinite periods of at least sufficient to insure adequate suspension stability during storage and shipment under normal industrial conditions.

References Cited in the file of this patent UNITED STATES PATENTS 1,924,281 Jagschitz Aug. 29, 1933 2,296,401 Perkins Sept. 22, 1942 2,623,903 Weaver et a1. Dec. 30, 1952 2,643,251 Staab et al. June 23, 1953 2,744,059 Mayer May 1, 1956 

1. AS A NEW COMPOSITION OF MATTER A STABLE, NON-CAKING, MACROSCOPICALLY HOMOGENEOUS-APPEARING CREOSOTE OIL CONTAINING BETWEEN ABOUT 0.5% AND ABOUT 5% (DRY BASIS) OF "ANTHRACENE SALT" CRYSTALS HAVING MAXIMUM PARTICLE DIAMETERS NOT EXCEEDING ABOUT 15 MICRONS AND HAVING THE PROPERTY OF REMAINING SUBSTANTIALLY NONCAKING UDER CONDITIONS OF TEMPERATURE FLUCTUATIONS BELOW THE LIMPID POINT OF THE OIL FOR INDEFINITE PERIODS AT LEAST SUFFICIENT TO INSURE ADEQUATE SUSPENSION STABILITY DURING STORAGE AND SHIPMENT UNDER NORMAL INDUSTRIAL CONDITIONS. 